The invention discloses a dynamic memory refreshing method and a refreshing controller, and belongs to the technical field of semiconductor memories. According to the dynamic memory refreshing method, based on a grain unit memory, by using a manner than the grain memory unit has two groups of mutually independent word lines and bit lines, read/write operation of external access is completed within an upper-half period of a clock, and refreshing read/refreshing write operation is completed within a lower-half period of the clock. According to the dynamic memory refreshing method, a refreshing request signal and a refreshing state signal are generated according to a refreshing period of the gain unit, a line number of a memory Bank and a clock period; control signals of corresponding refreshing read and refreshing write operations are generated according to a refreshing state to control refreshing read and refreshing write operations and external read/external write operation to be performed in parallel. According to the dynamic memory refreshing method, the confliction between a refreshing operation and the external access is eliminated, so that the memory can be accessed completely randomly in real time.